Generally, semiconductor devices are used in a variety of electronic applications, such as computers, cellular phones, personal computing devices, and many other applications. Home, industrial, and automotive devices that in the past comprised only mechanical components now have electronic parts that require semiconductor devices, for example.
Semiconductor devices are manufactured by depositing many different types of material layers over a semiconductor workpiece or wafer, and patterning the various material layers using lithography. The material layers typically comprise thin films of conductive, semiconductive, and insulating materials that are patterned and etched to form integrated circuits (ICs). There may be a plurality of transistors, memory devices, switches, conductive lines, diodes, capacitors, logic circuits, and other electronic components formed on a single die or chip, for example.
Optical photolithography involves projecting or transmitting light through a pattern comprised of optically opaque areas and optically clear or transparent areas on a mask or reticle. For many years in the semiconductor industry, optical lithography techniques such as contact printing, proximity printing, and projection printing have been used to pattern material layers of integrated circuits. Lens projection systems and transmission lithography masks are used for patterning, wherein light is passed through the lithography mask to impinge upon a photosensitive material layer disposed on a semiconductor wafer or workpiece. After development, the photosensitive material layer is then used as a mask to pattern an underlying material layer. The patterned material layers comprise electronic components of the semiconductor device.
There is a trend in the semiconductor industry towards scaling down the size of integrated circuits, to meet the demands of increased performance and smaller device size. However, as features of semiconductor devices become smaller, it becomes more difficult to pattern the various material layers because of diffraction and other effects that occur during a lithography process. Lithography techniques such as immersion lithography and EUV lithography have been developed or are currently under development to address the lithography challenges of decreased feature sizes. Immersion lithography is expected to enable the numerical aperture (NA) of the projection lens system to be greater than 1, for example.
A recent development in lithography is the use of polarized light for the exposure process. Problems resulting from the polarization of light and benefits arising from the intentional use of polarized light have become matters of interest, particularly with high NA patterning, such as in immersion lithography.
What are needed in the art are lithography masks and methods of manufacture thereof that are effective in exposure processes involving polarized light.